<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        img:hover {
            cursor: pointer;
        }
    </style>
    <script>
        function changeImage() {
            document.getElementById("kaptcha").setAttribute("src" , '/kaptcha?' + new Date());
        }
    </script>
</head>
<body>
<form method="post" action="/login">
    name:<input><br/>
    pass:<input><br/>
    验证码：<input name="code"><img onclick="changeImage()" id="kaptcha" src="/kaptcha"/><br/>
    <input type="submit" value="提交">
</form>

</body>
</html>